I'm sorry to hear you've suffered from narcissistic abuse. However, I strongly disagree with the label "evil" for anyone, especially for people diagnosed with NPD - this is a mental health issue. it's not helpful or productive to label those with mental health issues as evil. Let's label actions as destructive, hurtful or selfish, but not label the whole person as evil.

Of course you should protect yourself from the hurtful behaviour of others. If you find yourself trying to save someone with NPD (or anyone), then you probably have more healing to do on your own journey of self-discovery. The saviour complex is often a way to avoid your own inner work still left to do by focusing on the actions of another - this is something I've been guilty of.